Blockchain developer

What does a blockchain developer do?

A blockchain developer writes software that runs on a blockchain or talks to one.

The work covers smart contracts, the backend services around them and the tools that users touch. Singapore's job classification places the role under software developer.

You find the job in fintech firms, payment companies, crypto exchanges, banks and start-ups. Some larger companies also hire for digital asset and record-keeping pilots. Teams are often small, so one developer may cover contracts, tests and deployment.

A blockchain developer works with product managers, frontend and backend developers, security reviewers and compliance staff. In regulated firms, compliance and risk teams review features before they go live.

What the work involves

• Write and test smart contracts, usually in Solidity, and review teammates' contract code.
• Build the services and web interfaces that let users and other systems call those contracts.
• Run security checks and fix weaknesses found by tools, peers or outside auditors.
• Deploy contracts to test networks, then to live networks, and record what was released.
• Watch deployed contracts and supporting services, and respond when something breaks.
• Explain technical limits and trade-offs to product and compliance colleagues.

Pay in Singapore

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Skills a blockchain developer needs

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Blockchain developer job description

We are hiring a blockchain developer to design, build and maintain smart contracts and the services that connect them to our products in Singapore.

You will write tested, secure code, work with product, security and compliance colleagues, and take part in code reviews and releases. You should be comfortable with Solidity and at least one general-purpose language.

Responsibilities

• Design and write smart contracts that meet product and business requirements.
• Write unit, fuzz and integration tests, and keep test coverage high on critical contract logic.
• Build backend services and APIs, often in Go or TypeScript, that read from and write to the chain.
• Build or support web interfaces that connect users' wallets to the contracts.
• Find and fix security weaknesses, and work with external auditors on their findings.
• Manage deployments, contract upgrades and key handling with the infrastructure team.
• Monitor contracts and services in production and join incident response.
• Keep technical documentation and release records up to date in Git.
• Work with compliance and legal staff so features meet company policy and Singapore rules.
• Review pull requests and help junior developers improve their code.

Requirements

• A degree or diploma in computer science, engineering or a related field, or equivalent practical experience shown through projects.
• Typically 1 to 4 years of software development experience for a mid-level role. Entry-level roles may accept strong projects instead.
• Working knowledge of Solidity and how Ethereum-style chains handle transactions, gas and storage.
• Skill in JavaScript or TypeScript, and often Go or Rust, plus daily use of Git.
• Understanding of common attack types, such as reentrancy and access control mistakes, and of OWASP security guidance.
• A public portfolio, open-source contributions or audited work is a plus.

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Blockchain developer career path

Blockchain developers usually start as junior software developers and move up through technical depth, security skill and ownership of larger systems.

Titles vary by company, and many firms use general software engineer titles.

1. Junior blockchain developer

   Entry

   You write and test smaller contracts and tools under review from senior colleagues, and learn the team's security and deployment practices.

2. Blockchain developer

   Mid

   You own features from design to deployment, write contracts and backend services, and handle audit findings on your own code.

3. Senior blockchain developer

   Senior

   You design contract systems, set testing and security standards, and guide the work of other developers.

4. Lead blockchain engineer or engineering manager

   Lead

   You lead a team or technical area, decide on architecture and work with product, compliance and external auditors.

The titles are ones commonly used in Singapore; employers may name the levels differently.

Related jobs and their pay

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Blockchain developer interview questions

We wrote these questions from the skills this job needs. They are not an official question bank.

1. Walk through how a transaction goes from a user's wallet to being final on an Ethereum-style chain.

   What a good answer covers

   • The wallet signs the transaction with the user's private key.
   • The transaction carries a nonce and gas settings.
   • Nodes hold it in a pool until a block producer includes it.
   • Finality comes after more blocks or a finality mechanism.
   • Short chain reorganisations can reverse recent blocks, so apps wait for confirmations.

2. What is a reentrancy attack, and how do you prevent it in a Solidity contract?

   What a good answer covers

   • An external call lets the callee call back before state is updated.
   • Update state before making external calls (checks-effects-interactions).
   • Use a reentrancy guard on sensitive functions.
   • Prefer pull payments over pushing funds to users.
   • Test with a malicious contract that tries to re-enter.

3. How would you make a contract upgradeable, and what risks does that add?

   What a good answer covers

   • Explains proxy patterns that separate storage from logic.
   • Warns about storage layout clashes between versions.
   • Covers safe initialisation instead of constructors.
   • Notes that the upgrade key becomes a trust and security risk.
   • Suggests a multi-signature wallet and a timelock on upgrades, or no upgrades where possible.

4. A function loops over a growing array and gas costs keep rising. How do you fix it?

   What a good answer covers

   • Spots the unbounded loop as the root problem.
   • Replaces the array scan with a mapping or a running total.
   • Reduces storage reads and writes, and packs variables.
   • Moves work off chain and keeps only the proof or result on chain.
   • Measures gas before and after with test tooling.

5. How do you test a smart contract before it goes live?

   What a good answer covers

   • Writes unit tests for normal and failure paths.
   • Adds fuzz and invariant tests for rules that must always hold.
   • Tests against a fork of the live network where useful.
   • Deploys to a test network and rehearses the release steps.
   • Arranges an independent audit for contracts that hold value.

6. How do OWASP security practices apply to the web app and API around your contracts?

   What a good answer covers

   • Validates all input on the server, not only in the browser.
   • Applies access control to admin and operations endpoints.
   • Keeps keys and secrets out of code and logs.
   • Checks third-party packages for known vulnerabilities.
   • Makes wallet signing prompts clear so users know what they approve.

7. How would you use TypeScript when building a frontend that connects to a wallet and contracts?

   What a good answer covers

   • Generates typed contract interfaces from the ABI.
   • Checks that the user is on the right network before sending transactions.
   • Handles rejected signatures, pending states and failed transactions.
   • Checks values from the wallet or chain before trusting them.
   • Keeps contract addresses and settings in typed configuration.

8. When would you choose Go or Rust over Solidity on a blockchain project?

   What a good answer covers

   • Solidity is for contracts on Ethereum-style chains only.
   • Go suits indexers, node tooling and backend services.
   • Rust suits performance-sensitive code and chains whose programs are written in it.
   • Cites memory safety and concurrency as reasons to pick each language.
   • Considers what the team can maintain.

9. How do you manage Git branches and tags for a contract release that has been audited?

   What a good answer covers

   • Tags the exact commit the auditors reviewed.
   • Protects the release branch and requires reviews.
   • Reviews any change made after the audit and re-checks if needed.
   • Records the deployed address and commit together.
   • Keeps builds reproducible so the deployed code can be verified.

1. A bug is found in a live contract that holds user funds. What do you do in the first hour?

   What a good answer covers

   • Confirms the bug and measures how much is at risk.
   • Uses a pause or emergency control if one exists.
   • Alerts the security lead, management and compliance at once.
   • Prepares and tests a fix before releasing it.
   • Writes a post-incident report with root cause and prevention steps.

2. Your Go service that indexes chain events falls behind, and users see old balances. How do you find and fix the problem?

   What a good answer covers

   • Checks node or RPC provider limits and error rates.
   • Looks at database write speed and batch sizes.
   • Handles chain reorganisations without corrupting data.
   • Adds a backfill job and a lag metric with alerts.
   • Tells users when data may be delayed.

3. You use Claude Code to draft a contract function. How do you decide it is safe to merge?

   What a good answer covers

   • Reads every line and can explain what it does.
   • Writes or reviews tests, including fuzz tests, before trusting it.
   • Runs static analysis and compares against known attack patterns.
   • Keeps private keys, secrets and customer data out of prompts.
   • Sends the code through the normal peer review and audit process.

1. Tell us about a time an auditor or reviewer raised an issue you disagreed with. What happened?

   What a good answer covers

   • Describes the issue and your reasoning clearly.
   • Tests the claim with code instead of arguing from opinion.
   • Accepts the finding if the evidence supports it.
   • Explains the outcome and what changed in your process.

2. Describe a time you explained a blockchain concept to someone without a technical background.

   What a good answer covers

   • Names the audience and what they needed to decide.
   • Uses a simple example instead of jargon.
   • Is honest about limits and risks.
   • Checks that the listener understood and adjusts.

1. A product manager wants to store customer details on a public blockchain. How do you respond given the Personal Data Protection Act (PDPA)?

   What a good answer covers

   • Explains that public chain data is hard or impossible to delete.
   • Keeps personal data off chain and stores only hashes or references.
   • Asks what the product needs, and who is responsible for the data.
   • Raises the issue with the data protection officer or legal team.
   • Leaves legal conclusions to specialists and asks them to confirm.

2. Your firm plans digital token services for customers in Singapore. How do you work with compliance on Monetary Authority of Singapore (MAS) requirements?

   What a good answer covers

   • Asks compliance which rules apply before building.
   • Turns requirements into features, such as limits, logging and access control.
   • Keeps audit trails for transactions and admin actions.
   • Flags features that could change the firm's regulatory status.
   • Waits for compliance sign-off before release.

Common questions about a blockchain developer job

Sources